# coding=utf-8
import threading
from threading import RLock

# 可重入的锁

# 在同一个线程里面，可以连续调用多次acquire， 一定要注意acquire的次数要和release的次数相等
total = 0
lock = RLock()


def add():
    # 1. dosomething1
    # 2. io操作
    # 1. dosomething3
    global lock
    global total
    for i in range(1000000):
        lock.acquire()
        lock.acquire()
        total += 1
        lock.release()
        lock.release()


def desc():
    global total
    global lock
    for i in range(1000000):
        lock.acquire()
        total -= 1
        lock.release()


thread1 = threading.Thread(target=add)
thread2 = threading.Thread(target=desc)
thread1.start()
thread2.start()

#
thread1.join()
thread2.join()
print(total)

# 1. 用锁会影响性能
# 2. 锁会引起死锁
# 死锁的情况 A（a，b）
"""
A(a、b)
acquire (a)
acquire (b)

B(a、b)
acquire (a)
acquire (b)
"""
